The invention relates to a label identification system with a transmitting-receiving unit emitting a periodically alternating magnetic field through a primary coil and an identification label, which stores a digital identification information word on a bit basis and, fed by inductive coupling with the alternating magnetic field sent by the transmitting-receiving unit, outputs the stored identification information with a delay by corresponding modulation of the energy content of the transmission magnetic field, relates to an identification label which can be used for this and also relates to a coding method which can be used for such a label identification system.
Label identification systems consequently cover various types of applications, such as for example the identification of barcodes on price tags, the detection of identification information in stickers on cases for baggage distribution at airports or the identification of identification information in chip cards which are used for storing the amount of feed in intensive livestock farming. The identification labels used for this are commonly referred to as ID tags. In almost all cases, the identification labels are read wirelessly. Important criteria for the functionality of a label identification system is the range and positional dependence of the transmitting-receiving system. In this respect, on the one hand a great range and on the other hand a small positional dependence of the system are desirable. Moreover, the identification labels must in most cases (for example in hypermarkets) be produced at extremely low cost.
Furthermore, it is desirable whenever possible to apply the information to the identification labels only at the premises of the end user, and in the end to read this information reliably.
The prior art discloses label identification systems with great positional flexibility and range which have until now been produced as integrated silicon circuits with an integrated flash memory. On account of their relatively high price, such silicon circuits are suitable only for a small selection of applications, so that currently laser scanners are used at the supermarket checkout for the identification information that is applied to an identification label, for example in the form of a barcode, to be detected, de-inventorized and the price determined from it. Although, for this purpose, the barcodes to be applied to the label or the product can be printed on inexpensively, costing only fractions of cents, on the other hand the process of reading such barcodes takes place serially and is so far only possible at reasonable prices with human assistance.
It is accordingly desirable to provide a label identification system which operates electrically without human assistance, with identification labels which can be produced inexpensively. On the one hand an increasing number of label identification system applications would like to use the price advantages of mass production, but on the other hand the necessary precondition for this is that the integrated circuits required for the identification labels are produced much less expensively than at present. These requirements can only be partly satisfied by increases in productivity and smaller chip surface areas. The integrated silicon circuits with the low functionality necessary for many of these new applications would be limited however not by the scalable circuit but by the poorly scalable tags. Consequently, in order to open up new mass markets for label identification systems, the process on which the IC production is based must also be simplified.
An alternative for drastically lowering the production costs of integrated circuits consists from the current viewpoint in the use of novel, extremely inexpensive production processes, such as for example printed polymer transistors. In the simplest case, the circuits of the current integrated silicon circuits would in this case simply be transferred to a production process creating polymer transistors. However, this leads to a whole series of new problems. For example, it is not possible, at least from the current viewpoint, to produce powerful polymer-based n-MOS field-effect transistors, as are required for CMOS circuits. It must also be expected that, on account of the much poorer mobility of the charge carriers in the polymers, the power consumption of the polymer transistor circuits will be many times higher than that of the current CMOS circuits. Nonvolatile memories based on a polymer technique are likewise not available at present.